Two distinct factors interact with the promoter regions of several liver-specific genes.

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Abstract
A segment of the human alpha 1‐antitrypsin (alpha 1AT) 5′‐flanking region comprising nucleotides −137 to −37 from the start of transcription is sufficient to drive liver‐specific transcription from the homologous alpha 1AT promoter and from the heterologous SV40 promoter. In this paper we characterize two proteins, LF‐A1 and LF‐B1, whose ability to bind wild‐type and mutant alpha 1AT promoter segments correlates with the ability of these segments to activate transcription in vivo. DNase I protection and methylation interference analysis reveals that LF‐A1 recognizes sequences present in the regulatory region of the human alpha 1‐antitrypsin, apolipoprotein A1 and haptoglobin‐related genes. These sequences share a common 5′ TGG/A A/C CC 3′ motif. LF‐B1 binds to the palindrome 5′ TGGTTAAT/ATTCACCA 3′ which is present in the human alpha 1‐antitrypsin gene between positions −78 and −62 from the start of transcription. LF‐B1 also recognizes a related sequence present in the human albumin gene between −66 and −50. These results suggest that LF‐A1 and LF‐B1 are common positive trans‐acting factors which are required for the expression of several genes in the hepatocyte.